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  #1  
Old July 25th, 2007, 09:51
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meengreen meengreen is offline
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A/C cooling fan...

Where is the thermostat that activates the fan when needed? I want to replace it. Mine never kicks on. The A/C blows nice and cold until the truck gets warmed up, then blows warm. I checked and the r134 is at 34psi. Can't get much better than that.
Then I noticed the cooling fan never kicks on. I replaced the relay for the fan and that wasn't it either. Any other ideas what the problem could be?
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  #2  
Old July 25th, 2007, 10:07
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Re: A/C cooling fan...

what year model?
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  #3  
Old July 25th, 2007, 10:11
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Re: A/C cooling fan...

Oops, sorry. It's a 2001.
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  #4  
Old July 25th, 2007, 10:22
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Re: A/C cooling fan...

the fan will come on when the jeep exceeds 210* AND the head pressure on the AC compressor meets a minimum. Odd but true. The sensors that control it are the High side pressure sensor on the AC and the temp sensor in the thermostat housing. The ECU controls actual function when those sensors are tripped and activates the relay.

To test it you actually have to let the jeep get a little hot, probably at idle, in gear, on a sunny day.

If it is never working Have you tested the fan itself by bypassing the relay?
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  #5  
Old July 25th, 2007, 10:35
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Re: A/C cooling fan...

Thanks for the great info goodburbon.

Quote:
Originally Posted by goodburbon
To test it you actually have to let the jeep get a little hot, probably at idle, in gear, on a sunny day.

If it is never working Have you tested the fan itself by bypassing the relay?
As far as testing, the Jeep got up to operating temp. It was late dusk, maybe it wasn't hot enough? I do remember driving it the next day (wife uses it now) and the fan never came on. The high side tube off of the compresor was very hot. Couldn't even touch it for a second. My buddy says it shouldn't be that hot.
And no, I didn't check the fan itself yet. I did check for voltage at the fan and there was none. That's what made me think the relay or stat that controls on/off was bad. I'll hot wire the fan off the battery tonight and see what happens.
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  #6  
Old July 25th, 2007, 11:21
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Re: A/C cooling fan...

BS ALERT BS ALERT

The fan should kick on WHENEVER the AC turns on, and when the car gets to about 215-217.

Hotwire your fan to a battery and see if it works. IF not, replace. Ensure the connector is tight and uncorroded.

If you need a new fan, I posted a thread on here with a cheap, good solution.
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  #7  
Old July 25th, 2007, 11:28
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Re: A/C cooling fan...

Gotta link to that thread?...
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  #8  
Old July 25th, 2007, 11:47
Jess Jess is offline
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Re: A/C cooling fan...

you don't have to hotwire the fan.

unplug the temp sender on the thermo housing. It should kick on the check engine light and the fan should immediately come on.
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  #9  
Old July 25th, 2007, 12:01
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Re: A/C cooling fan...

Quote:
Originally Posted by Jess
you don't have to hotwire the fan.

unplug the temp sender on the thermo housing. It should kick on the check engine light and the fan should immediately come on.
Not to sound like to much of a dope, but where the heck is the temp sender and the thermo housing? I want to know what I'm doin', whilst I'm doin' it.
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  #10  
Old July 25th, 2007, 12:15
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Re: A/C cooling fan...

The tstat housing is where the upper hose and heater hose go into, on the front of the block.



Right dead in the center, except without any hoses attached to it in this pic. The black connector on the right is the temp sender. You can see it is unplugged in this picture. The fan should come on about 3-4 seconds after you unplug it if the engine is on.
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  #11  
Old July 25th, 2007, 12:20
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Re: A/C cooling fan...

Quote:
Originally Posted by darjevon
BS ALERT BS ALERT

The fan should kick on WHENEVER the AC turns on, and when the car gets to about 215-217.

Hotwire your fan to a battery and see if it works. IF not, replace. Ensure the connector is tight and uncorroded.

If you need a new fan, I posted a thread on here with a cheap, good solution.

Research a bit before you call BS. They changed the way they operate for the late models. I have a 97 and it comes on whenever the AC is on or when the jeep gets over 215. The wife's 2000 will only come on when the head pressure is high enough and/or the engine temperature is high. I thought hers was malfunctioning, brought it to the dealership and they charged me $60 to tell me that this was normal operation. I got the FSM for hers and sure enough if you look at the schematic it is true.
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  #12  
Old July 25th, 2007, 12:51
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Re: A/C cooling fan...

I'll try both ways. I really want to get the A/C working again. Thanks pauldo39, a picture is always worth a thousand words.
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  #13  
Old July 25th, 2007, 20:32
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Re: A/C cooling fan...

Quote:
Originally Posted by goodburbon
Research a bit before you call BS. They changed the way they operate for the late models. I have a 97 and it comes on whenever the AC is on or when the jeep gets over 215. The wife's 2000 will only come on when the head pressure is high enough and/or the engine temperature is high. I thought hers was malfunctioning, brought it to the dealership and they charged me $60 to tell me that this was normal operation. I got the FSM for hers and sure enough if you look at the schematic it is true.
Ok, my apologies. Any visual differences to the system?

Here's my electric fan alternative thread:

http://www.naxja.org/forum/showthread.php?t=920264
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  #14  
Old July 26th, 2007, 03:16
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Re: A/C cooling fan...

Thanks darjevon.
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  #15  
Old August 2nd, 2007, 15:57
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Re: A/C cooling fan...

Quote:
Originally Posted by pauldo39
The tstat housing is where the upper hose and heater hose go into, on the front of the block. The black connector on the right is the temp sender. The fan should come on about 3-4 seconds after you unplug it if the engine is on.
I checked right when my wife got the truck home from work. I figured I'd need to check it whil it wasn't working properly. I unplugged the sensor and the fan came on, just like you said it would. I also figured I'd try blocking the heater hoses. I clamped both, thinking that maybe the hose valve is bad and was feedeing hot air that was counter acting the cold. That wasn't it either. Then I checked the freeon charge. It was 120psi!! Then I realized the compresor wasn't kicking on at all. I think I narrowed the problem down to the compressor failing to kick on after it's hot. My question now is, why would it stop kicking on after the truck is hot? You guys have been a big help so far, and I appreciate it very much.
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